“Polyurethanes are formed by reacting a polyol (an alcohol with more than two reactive hydroxyl groups per molecule) with a diisocyanate or a polymeric isocyanate in the presence of suitable catalysts and additives.”
The commercial development of Polyurethanes began initially in Germany in the end of the thirties, with the production of rigid foams, adhesives and coatings. Polyurethane elastomers originated in the forties, in Germany and England. During Second World War the development of Polyurethane’s was discontinued, however since 1946 enormous growth could be observed in this market. The fifties registered the commercial development of Polyurethanes as flexible foams. During the sixties, the use of chlorofluorocarbons (CFC’s) as blowing agents in rigid foams resulted in extended use of this material in thermal insulation. In the seventies the semi-flexible and semi-rigid molded foams covered with thermoplastic materials were broadly used in the automotive industry. In the eighties, a commercially relevant technique, reaction injection moulding was developed, giving impulse to studies on the relationships between molecular structure and properties of Polyurethane’s. Due to environmental concern, in the nineties and in the beginning of the present millennium, researches have been directed to the substitution of CFC’s considered harmful to the layer of terrestrial ozone, so that systems have been developed which are free of volatile organic compounds (VOC’s), as well as placing more emphasis on Polyurethane recycling.
Polyurethane products have many uses. Over three quarters of the global consumption of polyurethane products is in the form of foams, with flexible and rigid types being roughly equal in market size. In both cases, the foam is usually behind other materials: flexible foams are behind upholstery fabrics in commercial and domestic furniture; rigid foams are inside the metal and plastic walls of most refrigerators and freezers, or behind paper, metals and other surface materials in the case of thermal insulation panels in the construction sector. The precursors of expanding polyurethane foam are available in many forms, for use in insulation, sound deadening, floatation, packing material, and even cast-in-place upholstery padding. Since they adhere to most surfaces and automatically fill voids, they have become quite popular in these applications.
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